1. Field of the Invention
The present invention relates to a method and an apparatus for measuring blood pressure of a subject based on pulse wave detected by a pulse wave sensor pressed against an arterial vessel.
2. Discussion of the Prior
There is known the "oscillometric" method as a method of measuring blood pressure. In the oscillometric method, a bag-like, rubber inflatable cuff is set around an upper arm of a subject, and pressurized air is supplied to the cuff to increase pressure in the cuff (hereinafter, referred to as `cuff pressure`) and thereby press the upper arm, so that pulse wave, i.e., oscillatory pressure wave produced synchronously with heartbeat of the subject is detected while the pressure in the cuff is increased. Blood pressure of the subject is determined based on the detected magnitude variation of the pulse wave.
In the above-indicated conventional method, an inflatable cuff is used for pressing the upper arm or other body portions of the subject. The cuff has a comparatively large size or volume, and therefore is bothersome to the subject, particularly in the case where the cuff is maintained on the body portion for a long time. Furthermore, since the cuff has a bag-like structure and, when used, is wound around the body portion of the subject, the cuff pressure tends to be adversely influenced by, for example, physical motion of the subject. In such case, the accuracy of blood pressure measurement is deteriorated.
In the case where the cuff is maintained around the body portion of the subject to monitor, i.e., continuously measure blood pressure of the subject for a comparatively long period after a surgical operation, for example, the subject may suffer from congestion and/or uncomfortable feeling because the body portion continues to be pressed with considerable force for that period.